Pyridone derivatives



Patented Nov. 28, 1950 PYRIDONE DERIVATIVES William F; Bruce, Upper Darby, Pa., assignorto Wyeth Incorporated, Philadelphia, Pa., a corporation. of Delaware No Drawing. Application. April 3, 1945, Serial No. 586,441,

6Claims.v 1,v

This invention is concerned with the preparation of intermediates useful in the synthesis of vitamin B6 and of somewhat similar compounds having a beneficial physiological action. The invention is particularly concerned with the preparation of newderivatives of 4-alkoxymethyl-6-methyl-2-pyridone-3-carboxylic acid of the group consisti'ng'of alkylesters of 4-alkoxymethyl halogeno 6 methyl- 2 pyridone 3 carboxylic acid and amides of 4-alkoxymethy- 5 halogeno 6 methyl 2 pyridone 3 car boxylic acid;

The following specific examples are illustrative of the compounds of thev invention and suitable methods for their preparation.

EXAMPLE I Preparation of ethyl 4ethorymethyl-fi-methylr. 2-pyridone-3-oarhorylate 113 g. (1 mol) of ethyl cyano acetate was added to 500 cc. of, ethyl alcohol in a flask equipped with a reflux condenser. 135 g. (1 mol) of ethoxy acetyl acetone-and 150 cc. of piperidine were added to the solution and the whole mixture was refluxed for three hours. After cooling in the refrigerator overnight'to allow the reaction product to precipitate, the ethyl 4-ethoxymethyl- 6-methyl-2pyridone-3-carboxylate was filtered off and the filtrate concentrated to a volume of 250 cc. An additional amount of the pyridone compound precipitated out from the concentrate upon cooling thoroughly. After recrystallization from alcohol, the yield amounted to 97 g. equal to 40% of the theoretical. The ethyl 4-ethoxymethyl-6-methyl-2-pyridone-3-carboxylate melts at 138 to 138.5 0., and crystallizes as fine very pale yellow needles which are soluble in hot alcohol, hot benzene and slightly soluble in hot water.

Analysis:

Calculated for: C12H11O4 60.23% C 7.16% H Found: 60.46% C 7.17% H Other alkyl esters of 4-alkoxymethyl-6-methyl-2-pyridone-3-carboxylic acid in which the alkyl group contains preferably not more than five carbon atoms, may be prepared in analogous manner by substitution of the appropriate cyano acetic ester.

EXAMPLE II Preparation of ethyl 4-ethozcymethyZ-5-bromo-6- methyl-2-pyridoae-3 oarboxyiate 24 g. (0.1 mol) of ethyl 4-ethoxymethyl-6 methy1-2-pyridone-3-carboxylate were dissolved in 150 cc. of glacial acetic acid and bromine added thereto until no more bromine was: taken up as evidenced by a permanent coloration. The

solution was then poured into 300- cc. of cold Analysis Calculated for C12Hl6O4NBI Found: 45.17 4.92

Other alkyl estersof 4-alkoxymethyl-5-bromo- 6-methyl-2-pyridone-B-carboxylic acid may be;

synthesized in an analogous manner by substitution of other alkyl esters of 4I-alkoxymethyl-6- methyl-2-pyridone-3-carboxylic acids prepared in a manner similar to the procedure described in Example I. Likewise the alkyl esters of 5- chloro 4 alkoxymethyl 6 methyl 2 pyri done- S-carboxylic acids and alkyl esters of 5- iodo 4 alkoxymethyl 6 methyl 2 pyri done-3-carboxylic acids may be prepared by treatment of the appropriate alkyl esters of 4- alkoxymethyl 6 methyl 2 pyridone 3 carboxylic acids with suitable chlorinating and iodinating agents.

EXAMPLE III Preparation of the amide of 4-ethoaymethyl- 5-bromo-6-methyl-2-pyridone-carboxylic acid 102 g. (1 mol) of malonamide and 600 cc, of alcohol were placed in a 2500 cc. round bottom flask equipped with a reflux condenser. g. (1 mol) of ethoxyacetylacetone and 200 cc. of piperidine were added to the malonamide solu' tion and the mixture was refluxed for a period of ten hours. The solution was then placed in an 2,532,055 IQ i icebox for several hours. The product which precipitated out was filtered off and recrystallized three times from 50% alcohol to free it from traces of malonamide. The yield of the amide of 4-ethoxymethyl-fi-methyl-2-pyridone-3-carboxylic acid amounted to 105 g. corresponding to 50% of the theoretical. The compound which crystallizes in fine white pellets, is insoluble in absolute alcohol, sparingly soluble in 95% alcohol, soluble in hot 50% alcohol and melts at 273 to 274 C.

Analysis:

Calculated for:

CmHmOaNa 57.12% C 6.71% H Found:

21 g. (0.1 mol) of the amide of l-ethoxy methyl-6-methy1-2-pyridone-3-carboxylic acid were dissolved in 200 cc. of glacial acetic acid and the solution was heated to 70 C. Bromine was then added to the solution until the solution turned permanently reddish indicating an excess of bromine. The solution was poured into 400 cc. of cold water and enough ammonium hydroxide was added to decolorize the solution. The precipitated bromo compound was filtered off and recrystallized from acetic acid. Upon drying, the yield of the amide of 4-ethoxymethyl-5-bromo-6- methyl-2-pyridone3-carboxylic acid amounted to 23 g. or 82% of the theoretical yield.

The amide of i ethoxymethyl bromo 6 methyl 2 pyridone 3 carhoXylic acid crystallizes in fine white matted needles, melts with decomposition at 310 C. and is slightly soluble in hot water and soluble in acetic acid.

Analysis:

Calculated for:

CH1303N2Br 41.53% C 4.53% H Found:

Likewise the amides of other l-alkoxy-methyl- 5-bromo-6-methy1-2-pylidone-3 oarboxylic acids may be prepared in an analogous manner by bromination of the appropriate 4alkoxy1nethyl-6- methyl-2-pyridone-3-carhoxylic acid. Substitution of suitable iodinating and chlorinating agents for bromine in the above procedures results in the amides of i-alkoXymethyl-5-bromo-6-methyl-2-pyridone-3-carboxylic acids and their amides of 4-alkoXymethyl-5-iodo-6-methyl-2-pyridone B-carboxylic acids.

The examples given above include the best em bodiments of my invention now known to me, but it is to be understood that the invention is not necessarily or specifically limited thereto and 5 may, under proper conditions, have other embodiments, produced in other ways without departure from the spirit of the invention and within the scope of the following claims.

What I claim is:

1. In the synthesis of a 5-bromo derivative of an alkyl ester of 4-alkoxymethyl6-methyl-2 pyridone-3-carboxylic acid, the steps of introducing elemental bromine into a solution of said ester in an organic solvent adapted to serve as a brominating medium until no more bromine is taken up by the ester, and recovering from the solution an alkyl ester of l-alkoxy-methyl-Eibromo-6-methyl-2-pyridone-3-carboxylic acid.

2. Compounds selected from the group consisting of the amides and the alkyl esters of 4.- alkoxymethyl 5-halogeno-6-methyl-2-pyridone- 3carboxylic acids.

3. Alkyl esters of 4-alkoXymethyl-5-ha1ogeno- 6-methyl-2-pyridone-3-carboxylic acids.

4. Amides of ei-alkoxymethyl-S-halogeno-6- methyl-2-pyridone-3-carboxylic acids.

5. Ethyl 4-ethoxymethyl-5-bromo-6-methyl- 2-pyridone-3-carboxylate.

6. 4 ethoxymethyl 5 bromo 6 methyl- 2-pyridone-3-carboxylic acid amide.

WILLIAM F. BRUCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Bruce, Journal American Chemical 800., Dec. 1944, pages 2092 to 2094.

Certificate of Correction Patent No. 2,532,055 I WILLIAM F. BRUCE It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 10, for 4-a1k0xymethyread 4-allaowymetkyb; line 42, for 0 111 0 read 0 E 0 1V and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 30th day of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents,

November 28, 1950 

2. COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF THE AMIDES AND THE ALKYL ESTERS OF 4ALKOXYMETHYL-5-HALOGENO-6-METHYL-2-PYRIDONE3-CARBOXYLIC ACIDS. 